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synth_device watchdog {

    ## How should the watchdog device decide that the watchdog has

    ## triggered, assuming the eCos application has failed to

    ## reset the device in time. There are two options: wallclock

    ## time, where the watchdog will trigger after a second

    ## irrespective of what the eCos application has been doing;

    ## or consumed cpu time, where the watchdog will only trigger

    ## if the eCos application has actually run for a whole second.

    ##

    ## Using wallclock time matches most real hardware,

    ## but can give spurious results if there are other processes

    ## running and consuming cpu cycles. Also, if the user has

    ## halted the application in gdb then the watchdog will trigger

    ## even though the application has no chance to reset the

    ## watchdog.

    ##

    ## Using consumed cpu cycles avoids these problems.

    ## However the default implementation of the idle thread action

    ## is to block in a select() system call, so if the eCos

    ## application spends most of its time idling but not resetting

    ## the watchdog then the device will not trigger. The

    ## configuration option CYGIMP_HAL_IDLE_THREAD_SPIN can be used

    ## to change the synthetic target HAL's implementation of the

    ## idle thread action.

    ##

    ## The default is to use consumed_cpu_time. Wallclock time can

    ## be selected by uncommenting the next line.

    # use wallclock_time

    # use consumed_cpu_time

    ## When running in GUI mode there will be a small window showing

    ## the current state of the watchdog: asleep, watching, or giving

    ## the alarm. This window can be packed as desired, using one

    ## of the container frames .main.nw .main.n .main.ne .main.w

    ## .main.e .main.sw .main.s or .main.se, and with a position of

    ## left, right, top or bottom. The default is to pack inside the

    ## .main.n frame, on the right, thus causing the watchdog to

    ## appear above the central text window.

    # watchdog_pack -in .main.n -side right

    ## If running in GUI mode, when the watchdog triggers and resets

    ## the eCos application this will be shown in the display.

    ## Optionally the watchdog device can also give an audible alert

    ## when this happens. This is disabled by default to avoid

    ## annoying co-workers, but can be enabled by specifying a suitable

    ## sound file. Two such files, sound1.au and sound2.au, are supplied

    ## with the watchdog device itself. Alternatively the user can

    ## specify a different sound file using a suitable path

    # sound sound1.au

    # sound sound2.au

    # sound ~/sounds/my_watchdog_alert.au

    ## If sound is enabled then the watchdog device needs some way to

    ## access the host's sound hardware. Rather than accessing

    ## /dev/audio or /dev/dsp directly the watchdog.tcl script will

    ## run an external program. This can avoid complications with

    ## different sound file formats etc. The default program is

    ## "play", a front-end to the sox utility, but a different

    ## program or script can be specified if desired. It will be run

    ## simply as "  &"

    # sound_player play

}